In LTE (Long Term Evolution), as shown in FIG. 9, radio base stations eNB#A/eNB#B are each configured to perform data transmission and reception with a mobile station UE communicating in a cell #A/#B under the radio base station eNB#A/eNB#B, by allocating a C-RNTI (Cell-Radio Network Temporary Identity) to the mobile station UE (see Non-patent document 1).
The C-RNTI is configured to be assigned on a cell basis. In LTE, as shown in FIG. 9, the same C-RNTI cannot be assigned to a mobile station UE#1 and a mobile station UE#2 which are communicating in the same cell #A, whereas the same C-RNTI can be assigned to the mobile station UE#1 (or the mobile station UE#2) and a mobile station UE#3 which are communicating in different cells #A/#B.
Note that the C-RNTI is configured to be assigned in a “Contention based RA (Random Access) procedure” or a handover procedure.
Further, the radio base station eNB is configured to assign resources for downlink data transmission and uplink data transmission by using the C-RNTI assigned to the mobile station UE.
At the 3GPP “Rel-12 workshop,” under the topic of FRA (Future Radio Access), many suggestions were made for “Small cell enhancement.”
Among those suggestions, a concept regarding a “phantom cell” is under consideration.
As shown in FIG. 10, unlike a conventional macro cell, a phantom cell is a single large cell formed by connecting many “small cells” to be able to cover a wide area.